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<H2>unary_function</H2>
<P><B>Module:</B>&nbsp;&nbsp;Standard C++ Library&nbsp;&nbsp;&nbsp;<B>Library:</B>&nbsp;&nbsp;<A HREF="2-4.html">General utilities</A></P>

<PRE><HR><B><I>Does not inherit</I></B><HR></PRE>

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<LI><A HREF="#sec1">Local Index</A></LI>
<LI><A HREF="#sec2">Summary</A></LI>
<LI><A HREF="#sec3">Synopsis</A></LI>
<LI><A HREF="#sec4">Description</A></LI>
<LI><A HREF="#sec5">See Also</A></LI>
<LI><A HREF="#sec6">Standards Conformance</A></LI>
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<A NAME="sec1"><H3>Local Index</H3></A>
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<A NAME="sec2"><H3>Summary</H3></A>
<P>Function object base class for creating unary function objects</P>
<A NAME="sec3"><H3>Synopsis</H3></A>

<PRE>#include &lt;functional&gt;

namespace std {
  template &lt;class Arg, class Result&gt;
  struct unary_function{
    typedef Arg argument_type;
    typedef Result result_type;
  };
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>Function objects are objects with an <SAMP>operator()</SAMP> defined. They are important for the effective use of the standard library's generic algorithms, because the interface for each algorithmic template can accept either an object with an <SAMP>operator()</SAMP> defined or a pointer to a function. The standard library includes both a standard set of function objects and a pair of classes that you can use as the base for creating your own function objects.</P>
<P>Function objects that take one argument are called <I>unary function objects.</I> Unary function objects are required to include the typedefs <SAMP>argument_type</SAMP> and <SAMP>result_type</SAMP>. The <B><I>unary_function</I></B> class makes the task of creating templatized unary function objects easier by providing the necessary typedefs for a unary function object. You can create your own unary function objects by inheriting from <B><I>unary_function</I></B>.</P>
<A NAME="sec5"><H3>See Also</H3></A>
<P><A HREF="functionobjects.html">Function Objects</A>, and <A HREF="../stdlibug/2.html">Chapter 2, "Iterators," in the<I> User's Guide</I></A></P>
<A NAME="sec6"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 20.3.1</I></P>

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